KR100260912B1 - Apparatus for processing image and for compensating image-error - Google Patents

Abstract

PURPOSE: An apparatus for correcting a distortion of a facsimile document is to eliminate a distortion in an analog-to-digital conversion of the facsimile document, thereby obtaining a high picture quality of the facsimile document. CONSTITUTION: An analog-to-digital conversion unit(300) converts an analog image signal of a facsimile document into a digital image signal using a control signal, a fluctuation range for adjusting a contrast and a fluctuation range for adjusting the brightness. A maximum reference voltage setup unit(310) sets up a maximum reference voltage in order for the analog-to-digital conversion unit to correct a distortion of the facsimile document. A minimum reference voltage setup unit(320) sets up a minimum reference voltage. A black color correction memory(340) and a white color correction memory(350) store a black color correction data and a white color correction data output from the analog-to-digital conversion unit, respectively. A maximum value detection unit(360) detects a maximum pixel data among the digital image data. A data storage unit(330) stores the output data of the maximum value detection unit.

Description

Device that performs image distortion correction and image processing

The present invention relates to an apparatus for performing image distortion correction and image processing, and more particularly, to correct digital image data by correcting distortion of an image reading sensor or a light source with respect to an analog signal proportional to the amount of reflected light according to the original state. The present invention relates to an apparatus for improving image quality of an output image by converting the image, and performing image distortion correction and image processing to obtain a sharp output image by contrast adjustment, brightness adjustment and background color removal of the original image.

In general, a scanner reflects light from a light source onto a document and reflects the reflected light to an image reading such as a charge coupled device (CCD) or a contact image sensor (CIS). The sensor converts it to an electrical output.

On the other hand, the converted output value generally serves to be stored in a data storage device such as a hard disk of a computer.

As such, a scanner that reads document contents such as documents and books may be manufactured as a single piece to be used exclusively for scanning, or may be configured as a single device of a multifunction apparatus together with a copy machine and a fax machine.

The analog signal output from the CCD sensor, a photoelectric conversion device of a general color image processing apparatus, includes variations due to individual differences between pixels of a CCD sensor, a semiconductor element, and emits light such as a fluorescent lamp or a halogen lamp used as a light source. And deterioration of image quality in reading an input image due to distortion of the white reference plate or the like.

In order to prevent the deterioration of the image quality due to such circuit elements and components, the color image input device performs black correction to correct individual differences according to the device characteristics of the CCD sensor, a light source (fluorescent lamp or halogen lamp) and a white reference plate. Back correction is performed to remove the effects of distortion.

In general, the distortion correction process of the color image input apparatus is composed of three steps.

First, black correction processing for acquiring black correction data that reads the magnitude of the dark current output from the pixel itself of the CCD sensor when no light is input to the CCD sensor, and subtracts the analog signal output from the CCD sensor by the correction data size. There are steps.

Next, there is a maximum value detecting step of applying power to the light source, performing black correction processing on the analog signal reflected on the white reference plate, and reading the maximum value of the output image signal.

Finally, the white light generated by applying power to the light source and detecting distortion of the light source and the white reference plate within the range of the maximum value detected in the maximum value detecting step and the black reference voltage for the analog signal reflected on the white reference plate. There is a back correction processing step of performing an operation of equalizing the correction data.

1 is a block diagram showing a circuit of a conventional preprocessor.

As shown, conventionally, while driving a CCD sensor in a state in which no power is applied to a light source and outputting an analog image signal, an analog-to-digital converter (abbreviated as 'A / D converter' hereinafter referred to as 'A / D converter') 201 ) Performs an operation for acquiring black correction data, and converts the analog image signal output from the CCD sensor into digital data within the range of the black reference voltage (V _Bref ) and the black maximum voltage (V _Bmax ) and converts it into digital data. Save at 202.

The black correction memory 202 has a capacity equal to the number of effective pixels of the CCD sensor, and the black correction data is sequentially stored according to the output synchronization signal of the CCD sensor.

Here, the A / D converter 201 operates to be used only in the black correction data detection operation.

Next, power is supplied to the light source so that the reflected light reflected on the white reference plate is input to the CCD sensor, and the data detected in the black calibration data detection operation is converted into a digital / analog converter (DAC: D / A converter or less). After converting the analog value into an analog value, the black compensator 204 performs a black correction operation by subtracting the magnitude of the black correction data from the output signal of the CCD sensor.

The analog image signal of which black correction processing is completed is input to the A / D converter 205 for detecting the maximum value, and converted into a digital value within the range of the white maximum voltage (V _Wmax ) and the black reference voltage (V _Bref ) and converted. The maximum pixel data value is detected by completing the comparison of the data with the maximum pixel data value detected just before the maximum value detector 206 to complete the maximum value detection operation.

Next, power is supplied to the light source so that the reflected light reflected by the white reference plate is inputted to the CCD sensor, and the black correction signal is input to detect the black reference voltage (V _Bref ) and the maximum value detector to detect the D / A converter ( The back correction data detection operation is performed by converting the digital data from the A / D converter 208 into the digital data within the back correction memory 209 within the range of the maximum small value V _PEAK of the converted back reference plate 207. do.

Therefore, in the case of performing the operation of reading the actual document image, the power is supplied to the light source so that the reflected light reflected on the original is input to the CCD sensor, and the analog signal output is converted into photoelectric conversion according to the reflected light to receive the black light. In order to perform the correction, data stored in the black correction memory 202 is provided to the black corrector 204 via the D / A converter 203 to perform a black correction operation.

In addition, in order to perform back correction, data stored in the back correction memory 209 is provided to the back corrector 211 through the D / A converter 210 to perform the back correction operation.

The distortion-corrected image signal is the black reference voltage (V _Bref ) and data bus which finally converted the data stored in the latch 215 through the data bus in the A / D converter 212 in the D / A converter 214. By converting the data stored in the latch 216 into digital image data within the range of the _white reference voltage V _Wref converted by the D / A converter 213, the operation of reading the original image as digital data is performed. .

Here, in the case of a color image input device that is currently being commercialized, a circuit for performing distortion correction processing, which is essentially used, is made into an application specific integrated circuit (ASIC). Applied as circuit elements.

In addition, conventionally, it has functions for contrast adjustment and brightness adjustment for image processing.

However, in the conventional image processing, the contrast adjustment of the original image and the brightness adjustment are performed by selectively specifying a predetermined value of a predetermined range as necessary, so as to determine the state of the original and to use the image input device as a reference. There was a difficulty to reset the optimum variable by changing the control program of.

Accordingly, the present invention was devised to solve such problems, and an object of the present invention is to remove peripheral distortion elements in converting an analog signal of an original image into digital.

In addition, a function for contrast adjustment, brightness adjustment and background color removal is added to a menu of a drive program operating on a computer according to the state of an original to output an optimal image for a function selected by a user.

1 is a block diagram showing a circuit of a conventional preprocessor;

2 is a block diagram showing a circuit of a preprocessor for performing the present invention,

3 is a system configuration diagram of an apparatus for carrying out the present invention.

4 is a flowchart showing image distortion correction and image processing procedures of an original according to the present invention.

<Description of the code | symbol about the principal part of drawing>

101: scanner control unit 102: ROM

103 RAM 104 Color CCD Sensor

105: buffer 106: amplification stage

107: multiplexer 108: memory buffer

109: interface 110: computer

111: sensor driver 112: lamp driver

113: lamp 114: step motor

115: optical module 116: preprocessor

201,205,208,212,300: Analog to Digital Converters

202,340: Black correction memory

203,207,210,213,214,315,316,324: Digital-to-Analog Converter

204 black compensator 206,360 maximum value detector

209,350 Back Correction Memory 211 Back Corrector

215,216,311,321,331,332,333: Latch

312,322: Adder 313: Black maximum voltage generator

314: back maximum voltage generator 317,325: analog switch

323: black reference voltage generator 310: upper limit reference voltage setting section

320: lower limit reference voltage setting unit 330: reference data storage unit

In order to achieve the above objects, an apparatus for performing image distortion correction and image processing includes a control signal input from a control unit of an image input apparatus, a variation for contrast adjustment and a variation for brightness adjustment. An A / D converter for converting analog image signals for originals detected and input by the image reading sensor of the image input device into digital data, and an upper limit for performing image distortion correction and image processing by the A / D converter. An upper limit reference voltage setting unit for setting a reference voltage, a lower limit reference voltage setting unit for setting a lower limit reference voltage for the A / D converter to perform image distortion correction and image processing, and an A / D converter in the A / D converter A black correction memory for storing black correction data output by performing a conversion operation, and outputted by performing an A / D conversion operation in the A / D converter A back correction memory for storing back correction data, a maximum value detector for detecting maximum pixel data values from digital image data output from the A / D converter, and reference data for storing data output from the maximum value detector; It includes a storage unit.

Preferably, the control signal is a black correction process for the black correction value generation mode selection signal for reading the magnitude of the dark current output from the pixel itself of the image reading sensor and the analog signal reflected to the white reference plate of the image input device. And a maximum value detection mode selection signal for reading out the maximum value of the output image signal, and detecting the distortion of the light source and the white reference plate of the image input device to equalize the original image. A value generation mode selection signal, a contrast adjustment mode selection signal for adjusting the contrast of the original, a brightness adjustment mode selection signal for adjusting the brightness of the original, and a background color removal mode selection signal for removing the background color of the original; It is characterized by.

Preferably, the background color removal mode selection signal is a signal for selecting the maximum value of the original of the original obtained in the pre-scanning mode as an upper limit reference voltage when the background color of the original is substantially constant, and the density of the background color in the original. If is different, it characterized in that it comprises a signal for selecting the minimum value in the main scan line of the image input apparatus as the upper limit reference voltage.

Preferably, the upper limit reference voltage setting unit includes a first D / A converter that receives a value output from the reference data storage unit, data output from the back correction memory, and contrast adjustment input from the control unit. A first adder which adds an upper limit variation, adds data output from the back correction memory, an upper limit variation for brightness adjustment input from the controller, and obtains an upper limit reference voltage, and a value output from the first adder A second D / A converter for converting into an analog signal, a constant voltage generator for generating an upper reference voltage for generating the black correction value and detecting the maximum value, the first D / A converter, and a second To set the upper limit reference voltage of the A / D converter among the data output from the D / A converter and the constant voltage generators. It characterized in that it comprises a first analog switch for selecting a value in accordance with the control signal group.

Preferably, the constant voltage generators include a black maximum voltage generator for generating an upper limit reference voltage for generating the black compensation value, and a white maximum voltage generator for generating an upper limit reference voltage for detecting the maximum value.

Preferably, the lower limit reference voltage setting unit includes a black reference voltage generator for generating a lower limit reference voltage for generating the black correction value, data output from the black correction memory, and a lower limit variation for contrast adjustment input from the controller. A second adder that adds to obtain a lower limit reference voltage, a third D / A converter that receives a value output from the second adder as an input, and converts it into an analog signal, the third D / A converter, and the black reference And a second analog switch for selecting one value according to the control signal to set the lower limit reference voltage of the A / D converter among data output from the voltage generator.

Preferably, the reference data storage unit includes: a first latch for storing a white reference plate maximum small value of the image input apparatus; a second latch for storing a maximum small value of an original obtained by prescanning the original; and the image input. And a third latch for storing the smallest maximum value in the main scan line of the device.

Hereinafter, the objects, features, and advantages of the present invention described above will be described in more detail with reference to the preferred embodiments of the present invention shown in the accompanying drawings.

2 is a block diagram showing a circuit of a preprocessor for performing the present invention.

First, the A / D converter 300 converts the analog output signal of the CCD sensor into a digital signal.

The black maximum voltage generator 313 generates the upper limit reference voltage while the A / D converter 300 performs the A / D conversion operation.

The back maximum voltage generator 314 generates an upper limit reference voltage while the A / D converter 300 performs an A / D conversion operation.

The black reference voltage generator 323 generates the lower limit reference voltage while the A / D converter 300 performs the A / D conversion operation.

The D / A converter 315 converts the maximum value of the white reference plate stored in the latch 341 into an analog voltage.

The D / A converter 316 converts the output value of the latch 311 which stores the variation controlled according to the image processing function selected by the user, and the output value of the adder 312 which adds the back correction data into an analog voltage.

The D / A converter 324 converts the output value of the latch 321, which stores the variation controlled according to the image processing function selected by the user, and the output value of the adder 322, which adds black correction data, to an analog voltage.

The analog switch 317 is configured according to a selection signal of an operation mode among the black maximum voltage generator 313 and the white maximum voltage generator 314, and output values of the D / A converter 315 and the D / A converter 316. Choose one.

The analog switch 325 selects one of the output values from the black reference voltage generator 323 and the D / A converter 324 according to the selection signal of the operation mode.

The black calibration memory 340 stores black calibration data output from the A / D converter 300.

The back correction memory 350 stores the back correction data output from the A / D converter 300.

The maximum value detector 360 detects the maximum value using the digital image data output from the A / D converter 300.

The latch 331 stores the maximum value of the back reference plate detected by the maximum value detector 360.

The latch 332 stores the maximum pixel value of the original.

The latch 333 stores the maximum value of the main scan line.

The first selection signal includes a black maximum voltage generator 313, a white maximum voltage generator 314, a D / A converter 315, and a D / A converter 316 according to the image distortion correction operation mode and the image processing operation mode. Select one of the data output from the set to the upper limit reference voltage, and selects one of the data output from the black reference voltage generator 323 and the D / A converter 324 to set the lower limit reference voltage.

The second selection signal selects one of the latch 331 and the data output from the latch 332 and the latch 333 according to the image distortion correction operation mode and the image processing operation mode to input the D / A converter 315. Provide by value.

3 is a system configuration diagram of an apparatus to which the present invention is applied and illustrates a color image input apparatus by way of example.

First, the scanner controller 101 generates a timing signal for performing a series of scan operations for reading an image of an original as digital data, transmits a selection signal according to an operation mode to the preprocessor 116, and inputs a color image. Control the overall operation of the device.

The ROM 102 stores a program and reference data having a certain flow so that the scanner controller 101 can control the scanner system in a predetermined order.

The RAM 103 stores temporary data generated while the scanner control unit 101 controls the system.

The lamp 113 outputs R, G, and B tricolor lights in order to read the image information of the document as the reflected light amount by the lamp driver 112 receiving the control signal from the scanner control unit 101.

The optical module 115 is configured to form a path so that the tricolor light output from the lamp 113 is reflected on the original and input to the photoelectric conversion element, and is focused on the color CCD sensor 104.

The step motor 114 receives the driving signal from the scanner controller 101 and moves the optical module 115 in the sub scanning direction of the original.

The color CCD sensor 104 photoelectrically converts color information of each of R, G, and B, which are three primary colors of light input through the optical module 115, into an electrical analog signal.

The sensor driver 111 receives a predetermined signal from the scanner controller 101 and supplies a clock signal to the color CCD sensor 104 so that the color CCD sensor 104 operates properly.

The buffer 105 transmits the analog signal output from the color CCD sensor 104 to the rear stage and prevents the distortion of the CCD sensor signal by the circuit of the rear stage.

The amplification stage 106 converts three color signals simultaneously input according to the signal of the scanner control unit 101 into output signals of a predetermined level, and amplifies them according to a predetermined amplification degree and connects them to the input of the multiplexer 107.

The multiplexer 107 selects one of three color information signals output from the amplifier 106 and connects it to the input of the preprocessor 116.

The preprocessor 116 receives the image signal selected by the multiplexer 107 and performs image distortion correction processing and image processing.

The memory buffer 108 temporarily stores the image data converted by the preprocessor 116 into digital data.

The interface 109 interfaces to transfer the image data stored in the memory buffer 108 to the computer 110 according to a certain transmission rule.

4 is a flowchart showing image distortion correction and image processing procedures of an original according to the present invention.

First, reference data for image distortion correction of an original image is generated, prescanned to detect the maximum value of the original (step S10).

The upper and lower reference voltages are set for contrast adjustment, brightness adjustment, and background color removal for the original image (step S20).

Image distortion correction processing for the original image using the reference data and image processing such as contrast adjustment, brightness adjustment, and background color removal are performed simultaneously on the original image using the set upper and lower reference voltages. (Step: S30).

An original image that has undergone the image distortion correction processing and image processing is output as digital image data (step S40).

Hereinafter, an apparatus for performing image distortion correction and image processing of the present invention will be described in detail with reference to FIGS. 2 to 4.

The entire operation is divided into four operation steps, which are performed in the order of the black correction data generation operation, the maximum value detection operation, the back correction data generation operation and the original image reading operation.

First, as shown in FIG. 3 to perform the black calibration data generation operation, the first selection signal provided from the scanner controller 101 to the preprocessor 116 has a value of 0 and is shown in FIG. 2. The analog switch 317 and the analog switch 325 are provided to each of the analog switches 317 and 325. The selected value of each analog switch is input as the upper / lower reference voltage of the A / D converter 300.

That is, as shown in Table 1, when the value of the first selection signal is 0, the analog switch 317 is connected to the black maximum voltage generator 313 as the upper limit reference voltage of the A / D converter 300, The lower limit reference voltage is connected to the black reference voltage generator 323.

Therefore, in the black correction data generation operation, the A / D converter 300 digitally outputs an image signal input in the range of the black maximum voltage V _Bmax as the upper limit reference voltage and the black reference voltage V _Bref as the lower limit reference voltage. The operation is completed by converting the data into the black correction memory 340 sequentially (step S11).

Next, as shown in FIG. 3 to perform the maximum value detecting operation, the first selection signal provided from the scanner controller 101 to the preprocessor 116 has a value of 1 and as shown in FIG. 2. The values provided in the analog switch 317 and the analog switch 325 are selected as the upper and lower reference voltages of the A / D converter 300.

That is, as shown in Table 1, when the value of the first selection signal is 1, the analog switch 317 is connected to the back maximum voltage generator 314 as the upper limit reference voltage of the A / D converter 300, the lower limit As a reference voltage, the black correction data V _BLK converted from the black correction data output from the black correction memory 340 through the adder 322 and the D / A converter 324 is input.

Therefore, in the maximum value detection operation, the A / D converter 300 converts the image signal input in the range of the white maximum voltage V _Wmax as the upper limit reference voltage and the black compensation voltage V _BLK as the lower limit reference voltage to the digital data. To convert.

At this time, the black correction data stored in the black correction memory 340 is output through the D / A converter 324 and the analog switch 325 as the correction data for the corresponding pixel is output in synchronization with the pixel synchronization signal. The black correction is simultaneously processed in the A / D converter 300 by the black correction voltage V _BLK .

Here, the image data converted into digital data is input to the maximum value detector 360 to perform an operation of detecting the maximum value according to the large comparison with the previous pixel value (step: S12).

Next, as shown in FIG. 3 to perform the back correction value generation operation, the first selection signal provided from the scanner controller 101 to the preprocessor 116 has a value of 2 and as shown in FIG. 2. The analog switch 317 and the analog switch 325 are provided to each of the analog switches 317 and 325. The selected value of each analog switch is input as the upper / lower reference voltage of the A / D converter 300.

That is, as shown in Table 1, when the input value of the first selection signal is 2, the analog switch 317 is the white reference plate detected by the maximum value detector 360 as the upper limit reference voltage of the A / D converter 300. The value of the maximum value of the converted voltage through the D / A converter 315 is selected and input, and the black correction data output from the black correction memory 340 as the lower limit reference voltage is added to the adder 322 and the D / A converter 324. The converted voltage is selected and input through).

Therefore, in the operation of generating the back compensation value, the A / D converter 300 receives the image signal input in the range of the white reference plate maximum voltage V _PEAK as the upper limit reference voltage and the black correction voltage V _BLK as the lower limit reference voltage. Convert to digital data.

The digital data generated in the process is sequentially stored in the back correction memory 350 to complete the back correction data generating operation (step S13).

Next, the smallest value of the original is detected in the pre-scan mode which is performed in the previous operation of the original image reading mode (step S14).

When the above operation is completed, the color image input device is in a state where all preparation operations have been completed, and the reading operation of the original image can be actually started.

Here, before giving the command to perform the scan operation, the user processes the contrast adjustment operation, brightness adjustment operation and background color removal to improve the image quality according to the state of the original image in the device driving program executed in the computer 110. You can select the action.

When the original is fixed and the original reading operation is started, the first selection signal provided from the scanner control unit 101 to the preprocessing unit 116 is changed in accordance with the contrast adjustment operation, the brightness adjustment operation, and the background color removal operation. As shown, the values provided in the analog switch 317 and the analog switch 325 and selected in each analog switch are input to the upper and lower reference voltages of the A / D converter 300 (step: S20).

At this time, if the user-specified image processing operation is the contrast adjustment process (step S21), as shown in Table 1, the input value of the first selection signal has a value of 3.

Accordingly, the back correction data V _WHT output from the back correction memory 350 and the data (-mα) stored in the latch 311 through the data bus are added by the adder 312, and the upper limit reference voltage is added. It is input to the D / A converter 316 and used by the analog switch 317 (step S22).

In addition, the black correction data output from the black correction memory 340 and the data (+ mα) stored in the latch 321 through the data bus are added by the adder 322 to use D as the lower limit reference voltage. It is input to the / A converter 324 and selected by the analog switch 325 (step: S22).

Accordingly, the A / D converter 300 converts the input image signal in the range of the upper limit reference voltage (V _WHT -mα) and the lower limit reference voltage (V _BLK + mα) into digital data.

Where m is the contrast adjustment step.

The digital data generated in the process of reading the original image is simultaneously subjected to the black correction process by the black correction voltage, the back correction process by the black correction voltage, and the contrast adjustment process by the amount of change. An operation may be performed (step S30).

Assuming that the contrast adjustment step (m) is controlled in 128 steps on the back side and 128 steps on the black side, the contrast variation α can be obtained as follows.

α = maximum value of the white reference plate / 256

Here, in order to execute the contrast adjustment, if the user selects and performs an arbitrary adjustment step divided into (+) and (-) steps (here, 128 steps each), the brightness of the white side is further increased for the (+) step. The image is processed toward the brighter, and the image is processed toward the darker the brightness on the black side in the (-) step.

That is, if three steps are selected for the white side and four steps are selected for the black side, the white side variation amount is 3α and the black variation amount is 4α.

Accordingly, in order to select the upper limit reference voltage (V _WHT -3α) and the lower limit reference voltage (V _BLK + 4α) before the contrast adjustment process starts, the latch 311 stores a complement value of 3α through the data bus. The latch 321 stores data of 4α through the data bus.

In this manner, the value stored in the latch 311 is added to the back correction value by the adder 312, and then input to the D / A converter 316 to generate the upper limit reference voltage of the A / D converter 300. In order to output through the analog switch 317.

On the other hand, after the value stored in the latch 321 is added with the black correction value by the adder 322, it is input to the D / A converter 324 to generate the lower limit reference voltage of the A / D converter 300. In order to output through the analog switch 325.

At this time, if the user-specified image processing operation is the brightness adjustment processing (step S23), as shown in Table 1, the input value of the first selection signal has a value of three.

Accordingly, the back correction data V _WHT output from the back correction memory 350 and the data (± nβ) stored in the latch 311 through the data bus are added by the adder 312, and then A / It is input to the D / A converter 316 for use as the upper limit reference voltage of the D converter 300 (step: S24).

Further, the black correction data V _BLK output from the black correction memory 340 is input to the D / A converter 324 for use as the lower limit reference voltage of the A / D converter 300 (step: S24).

Accordingly, the A / D converter 300 converts the input image signal in the range of the upper limit reference voltage V _WHT ± nβ and the lower limit reference voltage V _BLK into digital data.

Since the digital data generated in the process is performed by the back correction voltage included in the upper limit voltage and the black correction process is simultaneously performed by the black correction voltage input as the lower limit voltage, a desired correction operation is performed. (N: beta)) to perform an image processing operation of brightness adjustment (step: S30).

Here, the value nβ latched from the data bus to set the upper limit reference voltage of the brightness adjustment operation is determined in the following manner.

In other words, the upper limit variation β used to adjust the brightness of the output image is the maximum small value V of the original acquired in the prescan mode performed by all operations of the original image reading mode from the maximum small value V _PEAK of the white reference plate. _PEAK ') is subtracted by dividing the result value by the number of brightness adjustment steps.

β = (Minimum value of the white platen-original maximum value of the prescan) / n

Here, n is the brightness adjustment step.

The variation of the upper limit value determined by the above equation is performed according to the user's output image brightness adjustment step.

That is, when the user wants to darken the output image, the upper limit reference voltage is increased to output the dark image.

For example, the upper limit variation amount 3β is stored in the latch 311 through the data bus and the adder 312 performs the back correction memory 350 in accordance with a user-specified brightness adjustment step (e.g., dark 3 steps). The upper reference voltage V _WHT + 3β is generated by adding the back correction data V _WHT output from the D-A converter 300 and provided to the A / D converter 300 via the D / A converter 316 and the analog switch 317. .

In addition, when the user wants to brighten the output image, the upper limit reference voltage is reduced to output the image brightly.

For example, according to a user-specified brightness adjustment step (e.g., five levels of brightness), a complementary value of the upper limit variation amount 5β is taken and stored in the latch 311 through the data bus.

The complement value of the change amount 5β and the back correction data V _WHT output from the back correction memory 350 are added by the adder 312 to subtract the change amount 5β from the back correction data V _WHT . Same result.

That is, the upper limit reference voltage V _WHT -5β is generated according to the above process and provided to the A / D converter 300 via the D / A converter 316 and the analog switch 317.

At this time, if the image processing operation specified by the user is the background color removal processing (step: S25), there are two processing methods.

That is, as shown in Table 1, the input value of the first selection signal has a value of 2.

Accordingly, the _smallest value (V _PEAK 'or V _PEAK '') of the original detected by the maximum value detector 360 is selected and input to the D / A converter 316 to perform background color processing through the analog switch 317. Generates an upper limit reference voltage (V _PEAK ′ or V _PEAK '') (step S26).

In addition, the latch 321 stores a value of 0, and the black correction data V _BLK output from the black correction memory 340 is input to the D / A converter 324 to perform background color processing through the analog switch 325. A lower limit reference voltage V _BLK is generated (step S26).

Accordingly, the A / D converter 300 converts the image signal input in the range between the upper limit reference voltage V _PEAK 'or V _PEAK ''and the lower limit reference voltage V _BLK into digital data.

Here, in order to remove the background color of the original image, the maximum value detector 360 detects the maximum value of the detected original upon prescan and uses the value stored in the latch 332 and the maximum in the main scan line. There is a method of detecting a value and using the value stored in the latch 333.

When the value stored in the latch 332 is used, the maximum value of the detected original is applied as the upper limit reference voltage for the entire document during prescan, and when the value stored in the latch 333 is used. In the original reading operation, the maximum value detected in the main scanning line before one line is applied as the upper limit reference voltage for the next line processing.

The above two methods can be realized by controlling the second selection signal according to a mode determined by the user.

In the A / D conversion, the lower limit reference voltage is applied with black correction data output from the black correction memory 340.

Here, the difference between the two modes described above will be briefly described.

If the background color of the target document to be read is generally uniform, it is advantageous to select and process the former mode. If the density of the background color is different in the original, it is more preferable to select and process the latter mode. You can get good results.

Here, the back correction operation is not performed during the background color removal process, which is because the output image when scanning for character recognition typically uses binarization image data, and thus the influence of the back correction process on each pixel. Rather, it depends on how precisely the background color is removed and how the binarization reference level is determined to simplify processing.

When the original reading operation is performed by setting the upper / lower reference voltage according to the above operation, the black correction process and the background color removal operation are performed at the same time, so that the desired correction process and the image processing operation can be performed with a simple circuit configuration (step: S30).

In accordance with the above operation, the data which has undergone image distortion correction and image processing on the original image is finally output as digital image data (step: S40).

Mode, high and low reference voltage according to input value of selector. division Selection value 0 One 2 3 3 2 Operation mode Create black correction value Maximum value detection Create Back Compensation Contrast adjustment Brightness adjustment Remove background color Upper limit voltage V _Bmax V _Wmax V _PEAK V _WHT -mα V _WHT ± nβ V _PEAK '' V _PEAK '' Lower limit voltage V _Bref V _BLK V _BLK V _BLK + mα V _BLK V _BLK V _BLK

Where m is the contrast adjustment step and n is the brightness adjustment step.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will appreciate that the present invention may be modified without departing from the spirit and scope of the invention as defined in the appended claims. It will be appreciated that modifications or variations may be made. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

As described above, according to the present invention, in the conversion of an analog signal from an original image to a digital signal, image distortion correction operation is performed by removing peripheral image distortion elements and removing contrast and brightness and background color from the original image. By performing various image processing operations, errors due to individual characteristics of circuit elements can be minimized, so that an excellent output image can be obtained.

In addition, since only one A / D converter can be used to perform the image distortion correction operation and various image processing operations, errors due to individual characteristics of the circuit elements can be minimized.

In addition, a stable operation can be obtained by simultaneously performing the black correction operation and the back correction operation.

In addition, since the above operations are performed individually or in association with each other, image processing of various effects can be performed with a simple operation.

Claims (7)

The analog image of the original detected and input by the image reading sensor of the image input apparatus using the control signal input from the control unit of the image input apparatus, the variation for contrast adjustment, and the variation for brightness adjustment input from the controller. An A / D converter for converting a signal into digital data; An upper limit reference voltage setting unit for setting an upper limit reference voltage for the A / D converter to perform image distortion correction and image processing; A lower limit reference voltage setting unit for setting a lower limit reference voltage for the A / D converter to perform image distortion correction and image processing; A black correction memory for storing black correction data output by performing an A / D conversion operation in the A / D converter; A back correction memory configured to store back correction data output by performing an A / D conversion operation in the A / D converter; A maximum value detector for detecting maximum pixel data values from the digital image data output from the A / D converter; And a reference data storage for storing data output from the maximum value detector. The method of claim 1, wherein the control signal is A black correction value generation mode selection signal for reading the magnitude of the dark current output from the pixel itself of the image reading sensor; A maximum value detection mode selection signal for performing a black correction process on the analog signal reflected by the white reference plate of the image input device and reading the maximum value of the output image signal; A back correction value generation mode selection signal for detecting distortion of a light source and a white reference plate of the image input apparatus and performing an operation of equalizing the original image; A contrast adjustment mode selection signal for contrast adjustment of the original; Brightness adjustment mode selection signal for adjusting the brightness of the original and And a background color removal mode selection signal for removing the background color of the document. The method of claim 2, wherein the background color removal mode selection signal is A signal for selecting the original maximum value of the original obtained in the pre-scan mode as the upper limit reference voltage when the background color of the original is constant, and main scanning of the image input device when the density of the background color in the original varies. And a signal for selecting the maximum value of the smallest value in the line as the upper limit reference voltage. The method of claim 1, wherein the upper limit reference voltage setting unit A first D / A converter receiving a value output from the reference data storage as an input; The upper limit is added by adding the data output from the back correction memory, the upper limit variation for contrast adjustment input from the control unit, and the upper limit variation for the brightness adjustment input from the data output from the back correction memory and the control unit. A first adder for obtaining a reference voltage; A second D / A converter which receives a value output from the first adder as an input and converts the value into an analog signal; Constant voltage generators generating upper limit reference voltages for generating the black correction value and detecting the maximum value; A first value that selects one value according to the control signal to set an upper limit reference voltage of the A / D converter among data output from the first D / A changer and the second D / A converter and the constant voltage generators; An apparatus for performing image distortion correction and image processing, comprising an analog switch. The method of claim 4, wherein the constant voltage generators A black maximum voltage generator for generating an upper limit reference voltage for generating the black correction value; And a white maximum voltage generator for generating an upper limit reference voltage for detecting the maximum value. The method of claim 1, wherein the lower limit reference voltage setting unit A black reference voltage generator configured to generate a lower limit reference voltage for generating the black correction value; A second adder for adding a data output from the black calibration memory and a lower limit variation for contrast adjustment input from the controller to obtain a lower limit reference voltage; A third D / A converter which receives a value output from the second adder as an input and converts the value into an analog signal; And a second analog switch for selecting one value according to the control signal to set the lower limit reference voltage of the A / D converter among the third D / A changer and data output from the black reference voltage generator. And a device for performing image distortion correction and image processing. The method of claim 1, wherein the reference data storage unit A first latch for storing a back reference plate maximized small value of the image input device; A second latch for storing a maximum value of the original obtained by prescanning the original; and And a third latch for storing a maximum small value in the main scan line of the image input apparatus.

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